金在现代海底热液系统中的分布及演化

发布时间：2018-05-01 01:24

本文选题：海底 + 热液系统　；参考：《地质论评》2017年03期

【摘要】：现代海底热液系统内冷海水的下渗和热液流体的上涌及由此引发的水岩反应驱动着金的循环演化,并可在海底形成极具经济前景的富金矿床。海底下覆基岩深部层位中的金会因为水岩反应而大量溶解迁移到热液流体中,金含量可比海水高千倍的热液流体在向海底表面运移过程中发生的相分离作用会进一步富集金,当遭遇冷海水发生混合作用后引发H_2S浓度和温度的降低,由此导致金因溶解度降低而从热液流体中迁移出来并赋存在一同形成的硫化物矿物中。海底硫化物中金含量的分布受到围岩性质和构造环境的控制,形成在岛弧和弧后环境中的硫化物一般比洋中脊环境中的硫化物的金含量高,而在相似构造环境下形成在长英质围岩系统和超镁铁质围岩系统中的硫化物其金含量比镁铁质围岩系统中的高。相对于高温阶段形成的黄铜矿,低温成因的黄铁矿和闪锌矿普遍更富集金。在分布最广的黄铁矿的晶格内,固溶体态金的溶解度受到砷含量的控制,当超过矿物的溶解度时则会出现纳米到微米级金颗粒聚合体。虽然热液硫化物中的金含量比热液沉积物高的多,但由于受其捕获效率的制约,随热液流体运移到海底表面的金还是有相当一部分最终随着羽状流扩散到了远端沉积物中或被海洋水体所接纳。若要更清晰甚至定量化地厘清金在现代海底热液系统中的迁移演化过程及控制因素,则微区、原位和高精度的实验方法、分析技术和模拟研究将是下一步工作的重点。
[Abstract]:The infiltration of cold sea water and the upwelling of hydrothermal fluid in modern submarine hydrothermal system and the resulting water rock reaction drive the evolution of gold circulation and form gold rich deposits with great economic prospects on the sea floor. Gold in the deep strata of undersea bedrock will be dissolved and migrated to hydrothermal fluid due to water-rock reaction, and gold will be further enriched by phase separation during the migration to the seabed surface of hydrothermal fluid with gold content thousands of times higher than that of seawater. When cold seawater is mixed, the concentration and temperature of H _ 2S decrease, which leads to the migration of gold from hydrothermal fluid and the occurrence of sulphide minerals formed together. The distribution of gold in submarine sulphides is controlled by the nature of surrounding rock and tectonic environment, and the sulphides formed in island arc and back-arc environments are generally higher than those in mid-ocean ridges. The gold content of sulfides formed in felsic and ultramafic surrounding rock systems is higher than that in magnesium-iron surrounding rock systems. Low temperature pyrite and sphalerite are generally more gold enriched than chalcopyrite formed in high temperature stage. In the lattice of the most widely distributed pyrite, the solubility of the solid solution gold is controlled by the arsenic content. When the solubility of the mineral exceeds the solubility of the mineral, there will be nanometer-sized to micron-sized gold particle polymers. Although the gold content in hydrothermal sulphides is higher than that in hydrothermal sediments, due to the constraints of their capture efficiency, There is still a considerable amount of gold transported to the seabed surface with hydrothermal fluid, and eventually the plume flows into the distal sediment or is accepted by the ocean body of water. If we want to clarify the migration and evolution process and control factors of gold in modern seafloor hydrothermal system more clearly and quantificationally, the microzone, in-situ and high-precision experimental methods, analytical techniques and simulation research will be the focus of the next step.
【作者单位】：国土资源部海洋油气资源与环境地质重点实验室青岛海洋地质研究所;海洋国家实验室海洋矿产资源评价与探测技术功能实验室;中国地质大学地球物理与空间信息学院;国家海洋局海底科学重点实验室国家海洋局第二海洋研究所;
【基金】：国家自然科学基金资助项目(编号:41506074) 国际海域资源调查与开发“十二·五”课题(编号:DY125-22-QY-25) 中国地质调查局海域天然气水合物勘查工程(编号:DD20160218)的成果~~
【分类号】：P618.51;P744

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